Weird Missing/Shaking but no CEL!

Posts specific to the 3.0 litre NA H6 engine

Weird Missing/Shaking but no CEL!

Postby Curare » Thu Apr 21, 2016 8:16 pm

Hey guy and girls and others, I recently hit a problem with my H6 Outback 4GEN (2003 so it's OOLLLD) where I was driving it home, and about halfway I noticed it shuddering ever so slightly under load (sort of felt like a CV).

I noticed that as I pulled up to a set of lights it was still doing it, (even when in P or N).

Getting home I looked around for anything falling off, everything is in order, but it's still lollopy on idle like it's missing but no CEL light has come up, like it should for a missfire.

I was thinking that maybe it's got a bad head gasket (it's done 295k) but no exhaust gas bubbles are appearing in the system.

I was thinking that maybe a coil pack is failing but that would show up as a CEL fault, right?

I'm a little stumped!

Thoughts?
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Re: Weird Missing/Shaking but no CEL!

Postby bigBADbenny » Fri Apr 22, 2016 7:11 am

Not necessarily if eg coilpack, IME.
If poss, carefully unclip the coilpack leads, twist the pins slightly with needle nose pliers to promote continuity, reseat.
You may need to unbolt & remove the cp's to do this.
Use a ziptie if the clip tang on the cp has failed, to keep the plug on the cp.
That's 2.5t advice. Or get the car logged n LV'd.
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Re: Weird Missing/Shaking but no CEL!

Postby BillyCorgi » Fri Apr 22, 2016 8:09 am

Junior developed an intermittent miss. Lacked power.

Turned out to be a bad connection at the engine connection harness plug.
The one on the rear of the engine.
Cylinder #4 injector signal was being lost.
The connector is a real bugger to close and "Click" home
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Re: Weird Missing/Shaking but no CEL!

Postby Curare » Fri Apr 22, 2016 8:40 am

Right, I'll go through and fiddle with the connectors on everything. And while I'm at it I might just check my earth leads.

Anything else I should look for?
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Re: Weird Missing/Shaking but no CEL!

Postby 666 » Fri Apr 22, 2016 4:39 pm

Check all the above and also the harmonic balancer. With the engine running get a torch and look at the crank pulley to see if it's wobbling. Otherwise get the ECU logged to see if anything is not right.

My two cents.

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Re: Weird Missing/Shaking but no CEL!

Postby bigBADbenny » Sat Apr 23, 2016 3:36 pm

Does the Alvs cause issues like avcs in the turbos? If so logging might reveal the issue.
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Re: Weird Missing/Shaking but no CEL!

Postby Curare » Tue Apr 26, 2016 10:17 am

Well, it's fixed but just how I can't honestly say.

I decided to do an ECU reset initally just to see whether it would fix it, and it didn't.

I drove it around (more like limped it) for about 10 minutes, go home and checked the codes, nada/zip nothing.

So in a fit fo frustrated rage I unplugged and repluged everything I could get my hands on, coilpacks, cam angle sensors, the main plug back on the back of the engine, and fired it up.

Instantly the shaking was gone, the ragged idle was gone and she's been running sweetly all weekend!

:shock:
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Re: Weird Missing/Shaking but no CEL!

Postby bigBADbenny » Tue Apr 26, 2016 1:10 pm

There you go. Try contact cleaner and the pin blade twist if it returns :)
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